This invention relates generally to aircraft interior equipment and, in particular, to aircraft cargo handling systems.
In 1957, the United States Air Force adopted a standardized system to facilitate cargo handling aboard military airlift aircraft. The Air Force cargo handling system is known as “Materials Handling Support System 463L” or simply “463L System.” A central component of the 463L system is the HCU-6/E pallet, sometimes referred to simply as the “463L pallet,” which is a standardized pallet, 108 inches wide by 88 inches long by 2¾ inches thick, typically made of aluminum plates top and bottom with a balsa wood core, framed on all sides by aluminum rails. The rails have 22 steel tie-down rings attached so that there are six rings on each long side and five rings on each short side. The rails also have notches approximately 1¼ inches deep by 2¾ inches wide evenly spaced approximately every 10 inches along all sides.
The aircraft cargo handling system itself typically comprises a roller conveyor system mounted to the floor the aircraft, which enables the pallets to be moved easily in and out of the aircraft cargo bay. A plurality of guide rails are mounted to the aircraft floor with their long axes oriented parallel to the longitudinal axis of the aircraft. The guide rails are spaced apart by a distance of slightly more than 108 inches or 88 inches so that a 463L pallet can be slid into the gap between the guide rails with the long edge of the pallet either longitudinal or transverse to the longitudinal axis of the aircraft, depending on the aircraft configuration. The guide rails themselves are typically inverted L-shaped or T-shaped in cross-section so that they provide both vertical and lateral restraint of the pallet(s) positioned between the guide rails. Larger aircraft may have three or more guide rails, one each mounted near the port and starboard cabin walls with one or more centrals rail running along the center of the cabin floor.
The aircraft cargo handling system must also include a locking mechanism that is capable of locking the pallets in place longitudinally along the roller conveyor. In large aircraft, where there is space to move between the pallets, the locking mechanism may simply consist of a foot-operated cargo lock mounted to the floor of the aircraft between the roller conveyors. In smaller aircraft, such as military helicopters however, the locking mechanism typically must be situated in the very narrow confines between the guide rail and the cabin wall. Basic operation of the cargo system requires the pallets to be individually restrained and released sequentially front-to-back or back-to-front. The limited space available between the loaded pallets and the cabin wall makes it difficult to ascertain the locked or unlocked status of the individual cargo locks and also dictates that the locking and unlocking action be done from a remote location, where a human operator can fit.
U.S. Pat. No. 4,344,726 issued to Naffa discloses a cargo handling system including the right and left hand restraint rail assemblies having longitudinally spaced lock mechanisms which are positioned in the narrow space between the restraint rail assemblies and the cabin wall of a military helicopter. The lock mechanisms are capable of being sequentially locked and unlocked to provide longitudinal restraint of military 463L pallets. The cargo handling system of Naffa, however, is extraordinarily complex, consisting of multiple interconnected lock mechanisms, each of which includes dozens of moving springs, actuator rods, pivots, linkages, gear sectors, and other moving parts. What is needed is a cargo handling system having longitudinally spaced lock mechanisms that are capable of being sequentially locked and unlocked without the complexity and unreliability associated with the use of multiple interconnected lock mechanisms.